Chance of Down syndrome Noninvasive testing in first trimester...what is a low/high chance?

We just got our results back for our 12 week NIPT screening and they told us chance of having Baby with Down syndrome is 1/440... that number seems low to me? Specially in comparison to our results for trisomy conditions which was only 1/15,000 - what was your result if you were screened in the first trimester ?